Alkali metal alloy



Patented May 7, 1935 UNITED STATES PATENT OFFICE ALKALI METAL ALLOY Dorothy Hall Brophy, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York 3Claiml.

5 kali metals. More specifically this invention is concerned with a method of preparing such alloys and, particularly, a method of preparing caesium alloys.

Metallic caesium is dimcult to handle as such, due to its extreme reactivity in air. It has been desirable to obtain it in a form wherein it is relatively more stable than in the metallic state and yet easily decomposable to said state when desired. For example, in introducing the element in tubes, such as photo-electric cells, dimculty has been encountered due to the fact that the caesium oxidizes so readily and forms a layer of oxide thereon before it can be introduced into the tube, and special devices have been resorted to.for this purpose, such as the device shown in Letters Patent to Dorothy H. Brophy and William A. Ruggles, No. 1,685,666, dated September 25, 1928.

I have found that I can prepare alloys of caesium, the alloys being more stable and hence more easily handled than the metallic caesium itself, but, relatively speaking, sufficiently unstable in character so that the caesium may easily be obtained therefrom. Caesium alloys have not been prepared, as far as I am aware, direct from the metals because of the extreme reactivity of caesium in air. I have found that by employing certain precautions I can prepare caesium alloys direct from the metals.

For a consideration of what I believe to be novel and my invention, attention is directed to the following specification and the claims appended thereto.

The caesium employed in making the alloys may be easily prepared by reduction of caesium chloride with metallic calcium in a vacuum. A method which may be employed to obtain the caesium is disclosed in the Letters Patent above referred to. The metal is collected in a glass tube and covered with an oil such as a hydrocarbon oil or an organic liquid containing no hydroxyl group or groups which will react with caesium. An oil known to the trade as Nuioi may conveniently be employed for this purpose. As soon as the metallic caesium is covered with oil it may be exposed to the air.

The glass tube containing the caesium immersed in a body of oil is heated to approximately 60 C. The temperature may be kept at 50 C.- C. The metals to be alloyed may now be added. This is preferably done by adding the metals in the form of small pieces or shavings. The mixture is kept stirred and the caesium will be seen to change in color, becoming dark, and also becoming stifl and later breaking into fine particles.

The alloy which is formed is washed free of the oil with a substance such as petroleum ether and then may be transferred to aluminum cylinders. While stored for future use, the alloy is covered withan inert medium, such as petroleum ether, carbon tetrachloride and the like.

Various metals have been found which alloy with caesium and give it up during vacuum distillation. As examples of such metals may be cited lead, tin, zinc, cadmium, silver, strontium, magnesium and barium. Alloys containing more than one metal in addition to the caesium have also-been prepared by the method of the present invention. As examples of these, barium-aluminum-caesium and strontium-aluminum-caesium alloys are mentioned.

While I have described my invention as ap plied to caesium, I wish it to be understood that similar metals may likewise be used to form alloys in the manner outlined. For example, in place of caesium, I may employ rubidium, potassium and sodium. It will be understood that when such similar metals are employed the temperature of reaction will be different from that of caesium.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An alkaline earth metal-aluminum-caesium alloy which yields caesium on vacuum distillation.

2. A barium-aluminum-caesium alloy which yields caesium on vacuum distillation.

3. A strontiu'm-aluminum-caesium alloy which yields caesium on vacuum distillation.

DOROTHY HALL PHY. 

